RM6203 - switching PSU controller

[Chupacabras]

Hi,
is there anybody experienced with switched power supply circuits/controllers?

I am looking into RM6203 datasheet. There is some typical application.
1. But I don't understand what is the reason for capacitor C10
2. Is it isolated topology?

[lukaq]

1. is that Y cap or how it is called? must be for something else, since it is wired in wrong place
2. It is, you have transformer

[Chupacabras]

1. I do not think it s wired in wrong place. I found more circuits with cap wired like that.
2. There is transformer, but doesn't that cap bypass it? Couldn't it eventually pass some voltage to secondary?

[TonyBurroughs]

Maybe that cap is for bypassing high frequency signals to ground so if there was noise on the incoming line it won't show up on the output.
That's a guess though.

[lukaq]

2. There is transformer, but doesn't that cap bypass it? Couldn't it eventually pass some voltage to secondary?

2. Well yes, but no: it is wired to high DC voltage, with almost only low freq. ripple of low amplitude and it is very likely a small value cap, so it won't pass much anything

[Zero999]

It's a Y capacitor.

Yes, it is in the correct place.

It ensures both sides of the DC-DC converter are shorted together at high frequencies.

Without the Y capacitor, high frequencies will be coupled from the switching transistor to the secondary side via the inter-winding capacitance of the transformer.

The downside a small current from the mains can leak across the Y capacitor to the secondary.